Topic 8 - metals

Question 1

Properties of metals:

Answer 1

• High boiling and melting points
• hard and strong
• Malleable and ductile
• Conductors
• Sonorous
• Expand when heated

Question 2

what does malleable mean?

Answer 2

the metal can be hammered or bent into shape.

Question 3

what does ductile mean?

Answer 3

the metal can be drawn into wires

Question 4

what does sonorous mean?

Answer 4

the metal makes a ringing sound when struck

Question 5

How does metallic bonding work?

Answer 5

Each metal atom in the lattice donates its outer shell electrons to a ‘sea of electrons’ which are free to flow throughout the entire metal crystal.The metal atoms, having lost their outer shell electrons become positive metal ions.
The negative charge of the electron ‘sea’ sticks the positive metal ions together.

Question 6

Why do metals conduct well?

Answer 6

The delocalised electrons can move easily through the metal.

Question 7

Why are metals ductile and malleable?

Answer 7

Because the delocalised electron ‘glue’ is mobile, if the layers of atoms in the metal structure are forced to move over each other by hammering or stretching the metal they can still remain bonded together.

Question 8

What is an alloy?

Answer 8

Alloys are mixtures of two (or more) elements where at least one is a metal.

Question 9

Why are alloys often used over pure metals?

Answer 9

Alloys are often used instead of pure metals because alloys are often harder and stronger and have more useful properties.

Question 10

Give an example of an alloy

Answer 10

Brass - alloy of copper and zinc

Question 11

Why do alloys tend to be harder than pure metals?

Answer 11

The reason for the increased hardness of an alloy such as brass compared to the pure metal is that the positive ions of the different metals in an alloy have different sizes. This disrupts the regular lattice arrangement and makes it more difficult for the layers of ions to slide over each other.

Question 12

Reaction of metal and oxygen:

Answer 12

METAL + OXYGEN –> METAL OXIDE
Some metals react very fast with air (e.g. Na, K), so must be kept under oil.
Some react slowly (e.g. Fe, Zn).
Some do not react at all (e.g. Ag, Au). These metals are useful for jewellery.

Question 13

Reaction of metal and water:

Answer 13

METAL + WATER –> METAL HYDROXIDE + HYDROGEN GAS

Metals below magnesium in reactivity do not react with cold water at all

Question 14

Reaction of metal and steam:

Answer 14

METAL + STEAM –> METAL OXIDE + HYDROGEN GAS

aluminium, zinc and iron will react with steam in a similar manner to magnesium.

Question 15

Reaction of metal and acid:

Answer 15

METAL + ACID –> SALT + HYDROGEN
Effervescence (bubbling) will be observed
More reactive metals naturally react more quickly with acids than less reactive ones. The rates of reactions of less reactive metals (e.g. iron) with acids can be increased by heating, or using a form of the metal with a greater surface area, such as metal powder.

Question 16

Why does aluminium appear to react slowly with acid?

Answer 16

This is because a piece of aluminium metal has an unreactive surface coating of aluminium oxide which protects the metal below

Question 17

give order of metals in reactivity

Answer 17

Potassium - PLEASE
Sodium - SEND
Lithium - LITTLE
Calcium - CHARLIES
Magnesium - MONKEYS
Aluminium - AND
Carbon - CUTE
Zinc - ZEBRAS
Iron - IN
Lead - LEAD
Hydrogen - HARD
Copper - CAGES
Silver - SAFELY
Gold -GLORIA

Question 18

meaning of redox reaction:

Answer 18

If a metal is heated with the oxide of another metal, the more reactive metal will always end up combined with the oxygen.

Question 19

meaning of displacement reaction:

Answer 19

Displacement reactions occur between a metal and a solution of another metal’s salt. The more reactive metal will always end up combined. The less reactive metal is
displaced. Therefore reactions like this can be used to confirm the reactivity series of metals and also to place metals that are less familiar.

e.g. zinc + copper(II) sulphate –> zinc sulphate + copper
Zn(s) + CuSO4(aq) –> ZnSO4(aq) + Cu(s)

We say that the zinc has ‘displaced’ the copper from the solution of its salt.

Question 20

What is OILRIG

Answer 20

Oxidation is loss Reduction is gain

•Whichever metal is oxidised in a reaction looses electrons and whichever is reduced gains electrons.

Question 21

Give the equation for the extraction of mercury

Answer 21

mercury oxide ==> mercury + oxygen

HgO(s) ==> Hg(l) + ½O2

Question 22

Give the equation for the extraction of tin

Answer 22

SnO2(s) + 2C(s) ==> 2CO(g) + Sn(s) (Tin metal produced)

Metals that occur as sulphide ores (e.g. zinc and lead) undergo a two-stage process. The sulphide ore is first roasted in air to form the oxide, and then the oxide is reduced with carbon in the usual way:

e.g. 2PbS(s) + 3O2(g) ==> 2PbO(s) + 2SO2(g)
PbO(s) + C(s) ==> CO(g) + Pb(s) (Lead metal produced)

Question 23

How are very reactive metals extracted?

Answer 23

Via electrolysis

Question 24

What is the brown stuff on rusted iron called?

Answer 24

hydrated iron(iii) oxide

Question 25

what 2 factors are required for rusting to occur?

Answer 25

Presence of oxygen and water

Question 26

Give the equation for rusting

Answer 26

iron + oxygen + water ==> hydrated iron(III) oxide (rust)

2Fe(s) + 1½O2(g) + xH2O(l) ==> Fe2O3.xH2O(s)

Question 27

what makes rusting quicker

Answer 27

presence of salt or acid

Question 28

Explain how Coating/Plating reduces the rate of rusting

Answer 28

It prevents air and moisture coming in contact with the metal.

Question 29

Explain how Sacrificial Protection reduces the rate of rusting

Answer 29

By bolting blocks (‘anodes’) of magnesium or zinc onto steel structures. Zinc and magnesium are more reactive than iron, and lose electrons (are oxidised) more readily so the anode corrodes in preference to the steel structure.

Question 30

Explain how Galvanising reduces the rate of rusting

Answer 30

This involves coating steel objects like lampposts and dustbins with zinc. Since zinc corrodes to form a thin zinc oxide layer that resists further corrosion, it behaves as a barrier .

Question 31

Explain how Alloying reduces the rate of rusting

Answer 31

Metal objects can be manufactured using corrosion resistant alloys such as stainless steel;

Question 32

Give stages of iron ore extraction

Answer 32

1) The iron ore is crushed.
2) The iron ore is tipped into the top of
the furnace along with coke and
limestone.
3) Hot air is blasted in through pipes at
the base of the furnace. The coke
(carbon) reacts with the oxygen from
the air:

C(s) + O2(g) ==> CO2(g)

This reaction is very exothermic and helps to heat the furnace.
4) The carbon dioxide produced then reacts with more coke:

C(s) + CO2(g) ==> 2CO(g)

The carbon monoxide formed acts as the reducing agent in the process.
5) The carbon monoxide reduces (removes oxygen from) the iron ore to produce iron:

e.g. Fe2O3(s) + 3CO(g) ==> 2Fe(s) + 3CO2(g)

Question 33

why is limestone added

Answer 33

The limestone is added to the blast furnace to help. remove the impurities from the ore (mainly sand – silicon dioxide, SiO2). This occurs roughly as follows:
The limestone first decomposes in the heat of the furnace, producing calcium oxide (quicklime):

CaCO3(s) ==> CaO(s) + CO2(g)

Calcium oxide is a base and reacts with the acidic silicon dioxide to form calcium silicate, commonly known as ‘slag’:

CaO(s) + SiO2(s) ==> CaSiO3(l)

The molten slag runs to the bottom of the furnace where it floats on top of the molten iron (as it is less dense) and can be tapped off. Slag can be used for road building, foundations and cement making.